The invention concerns new organic silicon networks, a process for their production and use in silica-containing rubber compounds and vulcanizates manufactured from them.
An improvement in mechanical and dynamic properties is achieved by adding organic silicon compounds to silica-containing rubber compounds.
The production and use of alkoxysilane-containing compounds in rubber compounds to improve the mechanical and dynamic properties of the vulcanizates is known and described in numerous patents.
For example, the use of 3,3-bis(triethoxysilylpropyl)tetrasulfide in silica-containing rubber compounds improves the wet-slip resistance while at the same time reducing rolling resistance in comparison to carbon black-filled tire tread compounds. During the vulcanization process, the use of SiO2-containing fillers in conjunction with 3,3-bis(triethoxysilylpropyl)tetrasulfide leads to the formation of covalent rubber-filler bonds that provide an abrasion resistance comparable with that of tire tread carbon blacks (U. Gxc3x6rl, Gummi, Fasern, Kunststoffe, 1998, 51, 416-421).
3,3-bis(triethoxysilylpropyl)tetrasulfide is a typical representative of this class of compounds.
Although important rubber properties such as the above-mentioned dynamic properties are improved by the use of 3,3-bis(triethoxysilylpropyl)tetrasulfide, this improvement is achieved at the cost of substantially more complex compounding and processing in comparison to rubber compounds filled with carbon black. (H.-D. Luginsland xe2x80x9cProcessing of the Organo Silane Si 69xe2x80x9d The International Rubber Chemicals and Compounding Conference, 22nd-23rd Nov. 1999, Antwerp, Belgium).
For instance, silica-filled tire tread compounds containing 3,3-bis(triethoxysilylpropyl)tetrasulfide corresponding to the prior art are extremely susceptible to scorching and must, under no circumstances, exceed the temperature limit of 160xc2x0 C. during compounding.
Furthermore, little of the high silane content is actually utilized for the coupling reaction with the rubber matrix since a large part of the low-molecular silane disappears into the cavities caused by the microporosity and is unavailable for coupling to the rubber matrix. This means that the expensive silanes have to be used in high molar quantities. This, in turn, increases the cost of the filler system, i.e. silica plus silane, enormously in comparison to a carbon black system that does not require activation.
This, silica-filled tire compounds lead to restrictions in the compounding process, resulting in a decrease in productivity in the tire manufacturer""s entire production process, and at the same time, the cost of raw materials for the compound is dramatically increased by the low-molecular silane component.